RE: USB Ports not working and no PS2 ports available

Power off and remove power cord from rear of PC. Press/hold power button for ~30 sec. Reconnect power cord to rear of PC and boot up.

If that doesn't help, and you can't even press F2 to get into BIOS, you can try an externally powered USB hub with its own power brick. Plug the brick into the wall and the hub into a rear USB port. Connect mouse and keyboard through the hub.

Now power the PC on and see if mouse/keyboard are working again. If they work, there's a chance you might be able to do away with the powered hub. So post back if the hub works and we can go through the steps to try to eliminate it...